EMPORIA, Kan. (AP) - Tea-party challenger Milton Wolf confronted U.S. Sen. Pat Roberts during a walking tour in eastern Kansas on Wednesday, interrupting the senator's campaign stop to call attention to his refusal to have debates ahead of the Republican primary.

Roberts remains favored to win the Aug. 5 election and a fourth, six-year term in the November general election, but Wolf, a Leawood radiologist, contends he's closing the gap between them. Roberts came to Emporia to talk to small business owners.

The senator said earlier in the campaign that he was willing to have debates while noting that two other, lesser-known candidates also are seeking the GOP nomination. Then Roberts' executive campaign manager said earlier this month that the senator would not debate Wolf because of the challenger's "vague rhetoric and false attacks."

Wolf altered his schedule for a statewide bus tour to come to Emporia. Roberts had a brief meeting at the local chamber of commerce's offices and then, flanked by reporters, aides and about a dozen Wolf supporters, he walked downtown.

Wolf strode up to him at an intersection.

"You've told Kansans - you've given your word - you'd give a debate. You've said it multiple times at multiple places. You tell us that you're tough and tested and trusted," Wolf told Roberts as the group watched. "And I want you to keep your word. I want you to debate."

Roberts broke in, saying, "Milton, this is not the time. We have a regularly scheduled event, a listening tour event. This is not the way to conduct yourself."

Wolf argues that Roberts won't debate him because he's out of touch after a long career in Washington. He's attacked Roberts for owning a Washington-area home while listing his official residence as rented space in the Dodge City home of two supporters.

Roberts told reporters Wednesday that if Wolf won the primary, he could risk losing what has been a safe GOP seat. The senator's campaign is running statewide television ads highlighting news reports about a state medical board investigation of Wolf's past posting of X-ray images of fatal gunshot wounds and serious medical injuries, along with dark-humor commentary, on a now-disabled personal Facebook page in 2010. Wolf apologized in February.

In the street, Wolf pressed Roberts again about debates, and Roberts walked past him and into a downtown candy shop.

"Let a desperate candidate with an immature record and an unethical record pull stunts like this and let Sen. Roberts get down to the business he came here to do, all right?" Roberts spokesman Sean Fitzpatrick told reporters when the senator later resumed walking.

Then Roberts went into Dynamic Discs, a growing business selling equipment and clothing for Frisbee golf, where he took questions from local residents.

Wolf returned to his bus, which pulled out, honking its horn loudly several times as Roberts talked to people inside the store.

Afterward, Brandon Rains, a Wolf supporter from Emporia, said of Roberts, "I don't understand what he is afraid of in having a good, honest, open discussion with an opponent in a primary."